1. Field of the Invention:
The invention relates to high-voltage separable connectors and more particularly to loadbreak bushing inserts with piston-operated movable female contact assemblies propelled by the production of arc-quenching gases within such inserts during fault closure and activated operations.
2. Description of the Prior Art:
High-voltage separable connectors are intended to interconnect sources of energy such as transformers to distribution networks or the like. A typical arrangement includes a bushing well connected to the transformer, a bushing insert which contains a female contact assembly connected to the well and an elbow connected to a distribution line and containing the male contact to join the insert female contact. Because closure of the male and female contacts can occur under activated conditions or under fault conditions, the female contact is arranged to move within the insert to hasten the closure of the male and female contacts and thus extinguish any arc created. However, it is necessary to maintain electrical continuity during the travel of the female contact assembly. The connection between such female contact assembly and the remainder of the bushing insert must be flexible so as not to impede its movement but sufficient to carry the high currents in the circuit. Mechanisms for achieving these results have not always provided sufficient current paths causing the connectors to run hot, and interfering with proper operation of the distribution network and in the extreme leading to the destruction of the bushing inserts.
In U.S. Pat. No. 3,982,812, issued Sept. 28, 1976 to General Electric Company, there appears a bushing insert or module 1 which contains a metal cylinder 8 in which movable female contact 4 moves from a rest position to engage an inserted metal contact rod 10. Contact between the female contact 4 and the cylinder 8 during movement is maintained by flexible coiled conductor 5. Because of the need for flexibility and the space constraints inside the bushing insert or module 1, the size of the conductor is not optimum for current transfer under activated or fault closure conditions.
In U.S. Pat. No. 4,186,985 issued Feb. 5, 1980, FIGS. 1 and 2 of which appear as FIGS. 1 and 2 herein, and U.S. Pat. No. 3,930,709 issued Jan. 6 1976, FIG. 4 of which appears herein as FIG. 3, both patents being assigned to the assignee of the instant Application, there is shown a louvered contact ring or spring 34, 52. As is shown in FIG. 1, metallic sleeve 12 is electrically coupled to female contact assembly 30 by means of louvered spring 34 which encircles and is movable with piston 32 of the assembly 30. FIG. 3 shows that actual contact is achieved by the ends of the spring fingers 52b and 52c which respectively contact metallic sleeve 38 and the piston 50.
The quality and resistance of such contact is dependent upon the number of finger ends in contact and the amount of surface in contact. Distortion of the fingers, the presence of dirt or contaminants all decrease the amount of available contact area and influence the current density. Further, as the female contact assembly moves, the amount and quality of these contacts varies considerably.
This problem was treated and a substantial improvement made in the current transfer while the female contact assembly was in its initial position and in the initial stages of movement by providing a second contact operative at these times only to handle in a parallel path much of the high current present. However, once the female contact assembly was beyond its initial position, current transfer was again handled solely by the louvered contact ring or spring 34, 52 described above. This improved configuration is described and claimed in U.S. Pat. No. 4,773,872 issued Sept. 27, 1988, entitled "A Static Contact Member For A High-Voltage Bushing Insert" by Alan D. Borgstrom and assigned to the assignee of the instant application. FIG. 5 of that patent appears herein as FIG. 4.